html{
    font-size: 62.5%;
}

/*-----------------------------------------------------*/
/* PC用 */
/*-----------------------------------------------------*/
@media only screen and (min-width: 1200px) {
    body { 
        font-size: 1.8rem; 
    }
    h1 {
        font-size: 3.6rem;
    }
    h2 {
        font-size: 2.4rem;
    }
}


/*-----------------------------------------------------*/
/* タブレット用のCSS */
/*-----------------------------------------------------*/
@media only screen and (min-width:479px) and (max-width:768px) {
    body { 
        font-size: 1.8rem; 
    }
    h1 {
        font-size: 3rem;
    }
    h2 {
        font-size: 2.4rem;
    }
}


スマホ用のMedia Queries
/*-----------------------------------------------------*/
/* スマホ用のCSS */
/*-----------------------------------------------------*/
@media only screen and (max-width: 479px) {
    body { 
        font-size: 1.6rem; 
    }
    h1{
        font-size: 2.4rem;
    }
    h2 {
        font-size: 2rem;
    }
}